Conventional Stents
A wide range of medical treatments have been previously developed using “endolumenal prostheses,” which terms are herein intended to mean medical devices which are adapted for temporary or permanent implantation within a body lumen. Examples of lumens in which endolumenal prostheses may be implanted include, without limitation: arteries, such as for example those located within the coronary, mesentery, peripheral, or cerebral vasculature; veins; gastrointestinal tract; and fallopian tubes. Various different types of endolumenal prosthesis have also been developed, each providing a uniquely beneficial structure to modify the mechanics of the targeted lumenal wall. For example, various grafts, stents, and combination stent-graft prostheses have been previously disclosed for implantation within body lumen. More specifically regarding stents or stent-grafts, various designs of these prostheses have been previously disclosed for providing artificial radial support to the wall tissue which forms the various lumens within the body, and usually more specifically within the blood vessels of the body.
One more frequently disclosed “stenting” treatment beneficially provides radial support to coronary, peripheral, mesentery or cerebral arteries in order to prevent abrupt reclosure subsequent to recanalization of stenosed vessels, such as by balloon angioplasty or atherectomy (mechanical dilation of stenosed vessel by radial balloon expansion or direct removal of stenotic plaque, respectively). In general, the angioplasty or atherectomy-type recanalization methods reestablish flow to reperfuse tissues downstream of an initial stenosis. Subsequent to such recanalization, however, the dilated lumen of the stenosis site may reocclude, such as by abrupt reclosure (usually due to acute thrombosis or dissected vessel wall flaps transecting the vessel lumen), restenosis (generally considered as a longer term “scarring”-type response to wall injury during recanalization procedures), or spasm (generally considered a response to overdilatation of a vessel and in some aspects may be a form of abrupt reclosure). The implantation of stents to mechanically support the vessel walls at such stenosis sites, either during balloon angioplasty or subsequent to recanalization, is believed to deter the reocclusion of such recanalized vessels which may otherwise occur due to one or more of these phenomena. Various categories of stents have therefore arisen for the primary purpose of providing endolumenal radial support primarily within arteries adjunctively to recanalization.
One criteria by which various stent designs may be generally categorized draws from the structural design which forms a particular stent's tubular wall. Various “tubular wall” types of stents according to this criteria include, without limitation: wire mesh stents; coiled stents; tubular slotted stents; and integrated ring stents. In general, each of these “tubular wall” categories of stents includes a network of integrated support members which combine to form a tubular stent wall that defines a longitudinal passageway. The structural integrity of the integrated support members provides radial rigidity against physiological collapse forces at the vessel wall, whereas the longitudinal passageway through the prosthesis allows for perfused flow through the stented region.
Another criteria by which various stent “types” may be categorized relates to the delivery method by which a particular stent is adapted for implantation within a lumen or vessel. In general, stents are delivered in a radially collapsed condition to the stenting site via known percutaneous translumenal procedures. Once positioned at the stenting site, the stent is adjusted to a radially expanded condition which is adapted to radially engage the interior surface of the wall tissue which defines the lumen, such as a vessel wall in an arterial stenting procedure. According to this generally applicable delivery mode, various stent categories which may be stratified by more particular delivery methods include, without limitation: “self-expanding” stents, which generally expand under their own force once delivered to the desired stenting site; and “balloon expandable” stents, which generally expand under mechanical strain from an inflating balloon at the stenting site.
One specific example, within the previously disclosed “self-expanding” stents is adjustable from the radially collapsed condition to the radially expanded condition by removing a radial constraining member once delivered to the stenting site. This type of self-expanding stent is adapted to recover from an elastically deformed state, when radially confined by the constraining member in the radially collapsed condition, to a resting or recovered state in the radially expanded condition, when radially unconstrained. Further detailed examples of known constraining members for use in delivery systems for such known “self-expanding” stents include either radially confining sheaths or releasable tethers which are releasably coupled to the stent wall when in the radially collapsed condition. Another more specific example of a previously disclosed “self-expanding” stent is adjustable from the radially collapsed condition to the radially expanded condition by heating the stent once delivered to the stenting site, thereby inducing a heat-memory recovery of the stent to the radially expanded condition.
Further to the previously disclosed “balloon expandable” stent variations, known stents according to this type are generally crimped or otherwise held in the radially collapsed condition over an exterior surface of an expandable balloon and are adjusted to the radially expanded condition by inflating the balloon. Further detail of previously known “balloon expandable” stent designs includes those which are provided “pre-loaded” onto a balloon catheter, and also those which may be provided separately to a physician user who may crimp the stent onto a balloon immediately prior to delivery in vivo.
Further more specific examples of stents according to the various “tubular wall” and “delivery method” categories just summarized above are disclosed variously throughout the following references: U.S. Pat. No. 4,580,568 to Gianturco; U.S. Pat. No. 4,733,665 to Palmaz; U.S. Pat. No. 4,739,762 to Palmaz; U.S. Pat. No. 4,776,337 to Palmaz; U.S. Pat. No. 4,830,003 to Wolff et al.; U.S. Pat. No. 4,913,141 to Hillstead; U.S. Pat. No. 4,969,458 to Wiktor; U.S. Pat. No. 5,019,090 to Pinchuk; and in U.S. Pat. No. 5,292,331 to Boneau. The disclosures of these references are herein incorporated by their entirety by reference thereto.
Conventional Bifurcation Stenting Techniques
Stenoses within bifurcation regions of lumens, more particularly of arterial lumens, have long presented a particular challenge to conventional recanalization techniques, and more particularly to conventional stenting techniques. For example, adjunctively to implanting a stent within a main vessel, which includes a side-branch vessel arising from the main vessel wall along the implanted stent's length, additional stenting of the side-branch vessel may also be required in order to maintain patency of that vessel. The various clinical indications or concerns which are believed to give rise to the desirability of such bifurcation stenting include: mechanical closure of an acutely bifurcating side-branch due to angioplasty of the main vessel or implantation of the main vessel stent; additional stenotic disease in the side-branch vessel; and flow reduction and poor hemodynamics into the side-branch from the main vessel due to the occlusive presence of the main vessel stents structure in the entrance zone to the side branch. However, it is further believed that conventional stent designs present significant mechanical and procedural challenges to successful stenting of both the main and side-branch vessels at bifurcations of body lumens, and particularly within arterial bifurcations.
One conventional bifurcation stenting technique which has been previously disclosed includes first stenting the side-branch and then the main vessel. However, several challenges and incumbent risks related to this alternative method have been disclosed. For example, angle variations or limited angiographic visualization at the side-branch take-off may prevent accurate placement of the first stent exactly in the ostium of the side-branch, thereby resulting in a sub-optimal result in the ostium. Furthermore, placement of the first stent too far proximally at the take-off may occlude and prevent subsequent stenting of the main vessel.
Another conventional bifurcation stenting technique which has been previously disclosed includes first stenting the main vessel and then advancing a second stent through the wall of the main vessel stent and into the side-branch where it is deployed. However, this technique is also generally believed to be challenging due to the main vessel stent's tubular wall which occludes or “jails” the side-branch from access with the side-branch stent.
According to the challenges of conventional bifurcation stenting techniques just summarized, several modified stent deployment procedures have therefore been developed in attempt to safely and accurately implant conventional stents into both the main vessel and also the side-branch vessel at bifurcation regions of body lumens. In addition, particular stent designs have also been disclosed which are specifically intended for implantation within a bifurcation region and which are alleged to enhance the delivery of a second side branch stent using otherwise conventional techniques.
Modern Bifurcation Stenting Techniques using Conventional Stents
Several modern bifurcation stenting techniques which modify the use of conventional stents in bifurcation stenting procedures have been disclosed by David P. Foley et al. in “Bifurcation Lesion Stenting,” The Thoraxcentre Journal, Volume 8, Number 4 (December 1996), and include the “Monoclonal Antibody” approach; the “Culotte technique”; and the “Inverted Y” technique. The disclosure of this reference is herein incorporated in its entirety by reference thereto.
According to the “monoclonal antibody” approach disclosed in Foley et al., two guidewires are each delivered through an 8 French guiding catheter and into each of two branches at a bifurcation region, respectively, preferably using a 0.010″ guidewire in the side-branch at the bifurcation. Either the bifurcation lesion is dilated in each of the branch vessels separately, or in a “kissing” balloon technique wherein two balloons are simultaneously inflated in the branch vessels, usually with some balloon overlap in the proximal main vessel. Then, a stent of appropriate length is deployed into the main vessel, thereby “jailing” the 0.010″ wire in the side-branch vessel. Using the jailed 0.010″ wire as a radiopaque landmark, an additional wire, also preferably 0.010″ diameter, is then placed into the side branch through a gap between the support member of the main vessel stent's wall, after which the first “jailed” 0.010″ guidewire is removed. A dilatation balloon is then advanced over the second 0.010″ wire through the gap between the main vessel stent's support members, wherein the balloon is then inflated to dilate open the gap. A side-branch stent is then advanced through the dilated open gap and is deployed into the side-branch.
The “Culotte” technique disclosed in Foley et al. generally includes the following method. The first of two specific “Freedom” stents is implanted within the main vessel, including a first branch lumen of a bifurcation. A wire is then advanced through the side of the first stent and into the distal branch of the main vessel. The distal end portion of a second “Freedom” stent is then advanced over the wire and through the side of the first stent and into the second side branch lumen of the bifurcation, leaving the proximal end portio of the second “Freedom” stent within the proximal main vessel. According to this positioning, the second stent is implanted within both the second branch lumen and also in overlapping arrangement with the first stent in the main vessel. However, a risk of dissecting the side-branch is present in this technique because the side branch stent is oversized to that branch in order to properly engage the proximal main vessel.
According to the “Inverted Y” technique disclosed in Foley et al. and previously described by Antonio Colombo, two stents are each placed within first and second side branch lumens at a bifurcation region extending distally from proximal, main vessel lumen. Two guidewires are left in place within and through the implanted side branch stents. A third stent is then crimped onto two adjacent balloons which are adapted to track the indwelling guidewires to the proximal, main vessel lumen of the bifurcation region wherein the third stent is then implanted by expanding the two balloons adjacent to the first and second side branch stents. Further to the “Inverted Y” techniques just described, accurate positioning of each of three stents relative to the other stents is required, which may further require intracoronary ultrasound, and wire crossing particularly between delivery of the first two stents and the third stent may be a significant obstacle which may require a “test run” with the two balloon catheters prior to crimping the third stent thereover. Therefore, Foley et al. further discloses a modified variation of the “Inverted Y” technique, wherein the three stents described are together pre-loaded onto two long balloons such that the entire “bifurcation stent” may be placed in one manoeuvre. However, this modified variation is believed to by more bulky and rigid than the initial “Inverted Y” technique and may require very good predilatation and ideally a fairly proximally located and easy to reach bifurcation in reasonably large vessels.
Further disclosure of conventional stenting techniques is also provided by Freed, M. D., et al. in “The New Manual of Interventional Cardiology,” Chapter 10, pp 238–243, Physicians' Press, 1996. The disclosure of this reference is herein incorporated in its entirety by reference thereto.
Modern “Bifurcation Stents”
Particular stent designs have also been disclosed which are specifically intended for use within arterial bifurcation regions. More particularly, two stent designs which appear to be specifically designed for use within arterial bifurcation regions, respectively called the “SITOstentRS” and the “JOStentRB”, have been previously disclosed by “PENTACHI-SITOmed SrL” corporation located in Milan, Italy. In general, each of these particular stents includes a region along the stent tubular wall which has larger spaces or “side ports” between support members than are provided at other regions along the stent tubular wall.
More particularly regarding the previously disclosed “SITOStentRS,” the widely spaced side port region appears to be positioned along a midportion of the stent tubular body, wherein it is bordered on either side by a more tightly structured tubular wall. The “SITOStentRS” further appears to be adapted for positioning along a main artery such that the widely spaced side port region along its midportion is aligned with a side branch extending from the main artery.
In contrast, the previously disclosed “JOStentRB” appears to provide the widely spaced side port region along one end portion, which appears to be the intended proximal end portion, of the stent tubular wall. The “JOStentRB” further appears to be adapted for positioning within a bifurcation region such that a distal, tightly integrated support member portion is located within a first branch lumen extending from the bifurcation zone, and such that the proximal, widely spaced side port region extends across the entrance zone to a second branch lumen extending from the bifurcation region and is further positioned only partially within the more proximal main or common artery. It further appears from the prior disclosure of the “JOStentRB” that the alignment of the relatively widely spaced side port region with the entrance zone of the second side branch artery is adapted to facilitate delivery of a second stent, which may be a second “JOStentRB”, through one of those widely spaced side ports and into the second branch lumen for implantation adjacent to the bifurcation.
None of the cited references discloses an endolumenal prosthesis assembly with a tubular prosthesis body which is adapted for implantation within a bifurcation region of a body lumen such that a second prosthesis may be subsequently implanted within a side branch lumen extending from the bifurcation region along the length of the implanted tubular prosthesis body without the need to sub-select a side port along the tubular prosthesis body which is aligned with the side-branch and then deliver the second prosthesis through the sub-selected side port.
Nor do the cited references disclose an endolumenal prosthesis assembly with a tubular prosthesis body which is adapted for implantation within a main lumen of a bifurcation region of a body lumen, and wherein the prosthesis assembly is further adapted for preselecting a side port along the prosthesis body, prior to delivering the prosthesis body to a bifurcation region of a body lumen, which may then be aligned with one side branch lumen extending from the main lumen and through which a second prosthesis may be delivered and implanted within the side branch lumen.
Nor do the cited references disclose an endolumenal prosthesis assembly with a tubular prosthesis body which is adapted for implantation within a main lumen of a bifurcation region of a body lumen, wherein the prosthesis assembly further includes a dilator pre engaged within and through a side port along the prosthesis body prior to implanting the prosthesis body within the main lumen, and which is further adapted such that the side port and dilator may be aligned with a side branch lumen extending from the main lumen subsequent to positioning the prosthesis body within the main lumen but prior to implanting the prosthesis body within the main lumen.
Nor do the cited references disclose an endolumenal prosthesis assembly with a tubular prosthesis body which is adapted for implantation within a main lumen of a bifurcation region of a body lumen, wherein the prosthesis assembly further includes an access device which is pre-engaged within and through a side port along the prosthesis body prior to implanting the prosthesis body within the main lumen, and wherein the prosthesis assembly is further adapted such that the side port and access device maybe aligned with a side branch lumen extending from the main lumen along the length of the prosthesis body subsequent to positioning the prosthesis body within the main lumen but prior to implanting the prosthesis body within the main lumen.